Internal structure Model of Callisto's internal structure showing a surface ice layer, a possible liquid water layer, and an ice-rock interior Callisto's battered surface lies on top of a cold, stiff, and icy lithosphere that is between 80 and 150 km thick. [11] [17] A salty ocean 50–200 km deep may lie beneath the crust , [11] [17] indicated by studies of the magnetic fields around Jupiter and its moons. [31] [32] It was found that Callisto responds to Jupiter's varying background magnetic field like a perfectly conducting sphere; that is, the field cannot penetrate inside the moon, suggesting a layer of highly conductive fluid within it with a thickness of at least 10 km. [32] The existence of an ocean is more likely if water contains a small amount of ammonia or other antifreeze , up to 5% by weight. [17] In this case the ocean can be as thick as 250–300 km. [11] Failing an ocean, the icy lithosphere may be somewhat

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Unformatted text preview: thicker, up to about 300 km. Beneath the lithosphere and putative ocean, Callisto's interior appears to be neither entirely uniform nor particularly variable. Galileo orbiter data [3] (especially the dimensionless moment of inertia [h] 0.3549 0.0042determined during close flybys) suggest that its interior is composed of compressed rocks and ices , with the amount of rock increasing with depth due to partial settling of its constituents. [11] [33] In other words, Callisto is only partially differentiated . The density and moment of inertia are compatible with the existence of a small silicate core in the center of the satellite. The radius of any such core cannot exceed 600 km, and the density may lie between 3.1 and 3.6 g/cm 3 . [3] [11] Callisto's interior is in stark contrast to that of Ganymede , which appears to be fully differentiated....
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